If AIDS reduces the number of white blood cells, and hepatitis C increases the number of white blood cells, why are we not using hepatitis C as a cure for AIDS?
Because there’s more to each disease than that. You’re thinking that for every blood cell in one, the equal amount is lost with the other but that’s way too simplistic. AIDS shuts down the immune system, not just white blood cells. And that’s lots of various cells.
A better choice is lupus, which revs up the immune system vs Hep C, but that’s been tried and didn’t work. Or leukemia, which drastically increases white cells. But that doesn’t work for the same reason.
However, the recent AIDS patient who was “cured” was treated for cancer and now shows no signs of AIDS. That’s the second patient in many years so this effect hasn’t been readily replicated.